Short-term subjective and EEG responses following cervical rotatory manipulation are not reproduced by simulated cracking sound: A randomized controlled study

BACKGROUND: Cervical rotatory manipulation (CRM) is commonly used for neck-related symptoms and is often accompanied by a cracking sound. Whether a simulated cracking sound can reproduce the short-term subjective and neurophysiological responses to the complete CRM remains unclear. OBJECTIVE: This study compared short-term subjective and electroencephalography (EEG) responses to CRM with those following sham manipulation with or without a simulated cracking sound. METHODS: In this randomized controlled trial with three parallel groups and a single intervention session, 54 healthy volunteers were allocated to CRM, sham manipulation, or sham + simulated sound. Positive affect, negative affect, comfort, satisfaction, and eyes closed resting state EEG were assessed before and after the intervention. Prespecified EEG derived outcomes included frontal alpha power, frontal alpha/beta ratio, occipital individual alpha frequency, and alpha band frontoparietal and frontotemporal functional connectivity. RESULTS: CRM produced greater improvements in positive affect, comfort, and satisfaction than sham manipulation or sham + simulated cracking sound, whereas no clear difference among groups was observed for negative affect. Differences among groups were also observed in frontal alpha/beta ratio and alpha band frontoparietal and frontotemporal functional connectivity. Sham + simulated sound did not reproduce the overall pattern of subjective and EEG responses observed after CRM. CONCLUSIONS: CRM produced greater improvements over the short-term in positive affect, comfort, and satisfaction and was accompanied by differences in selected resting state EEG outcomes compared with sham manipulation with or without simulated cracking sound. Adding simulated cracking sound to sham manipulation did not reproduce this pattern. Because CRM differed from the control conditions in several procedural components, the specific component or combination of components responsible for these differences could not be determined. TRIAL REGISTRATION: The trial was registered with the International Traditional Medicine Clinical Trial Registry (URL: https://itmctr.ccebtcm.org.cn; ITMCTR2025001112).